1. Field
The present disclosure relates to a client device that receives electronic messages.
2. Description of the Related Art
There are two types of electronic messages which a client device can use to transmit and receive messages: carrier mail, in which a mobile phone operator provides its own domain, and Short Message Service messages (hereinafter designated SMS messages) which are transmitted using a phone number. Carrier mail is transmitted via an electronic mail server established by the operator, and messages can be transmitted not only among mobile phone client devices, but also to mobile phone client devices from various client devices able to access the Internet.
SMS messages are transmitted and received among mobile phone client devices via a message center set up by the operator. SMS messages may also be passed among multiple operators.
Carrier mail and SMS messages have respective merits and demerits. For this reason, users divide their usage of the two types of messages according to context. For example, a carrier mail message may be transmitted to a party whose carrier mail address is known, whereas an SMS message may be transmitted to a party for whom only a phone number is known. Carrier mail addresses can be changed comparatively easily by the user him- or herself. Also, since the domain differs for each operator, the carrier mail address is also changed in the case where the user changes his or her contracting carrier.
Meanwhile, since SMS messages use phone numbers as addresses, there is little likelihood of the address (phone number) being changed. Even in the case of changing operators, a mobile phone client device can keep the same phone number by utilizing a MNP (Mobile Number Portability) system.
PTL 1 describes an address list update process conducted in a mobile phone client device in the case of a change of mail address.